Enlarger



E. c. ROGERS 2 277 143 ENLARGER Filed Oct. 9, 1939 ZNVEN'FOR.

Patented Mar. 24, 1942 UNITED STATES PATENT OFFICE ENLARGER Elwood 0.Rogers, Indianapolis, Incl.

Application October 9, 1989, Serial No. 298,574

6 Claims.

My invention relates to photographic enlargers.

It is the object of my invention to eliminate reflections from the innersurfaces of the walls of the metallic enlarger-casing, so that the lightrays coming from unwanted points and tending to fog the image may beeliminated; and at the same time to lessen the inflow of heat into thosewalls, so that the enlarger will be cooler to handle and there will beless heat conducted to the lenses and other heat-sensitive parts of theenlarger, and especially to the negative.

In carrying out my invention, I coat the inner surfaces of theenlarger-casing walls with an adherent black flocculent material, whichserves to absorb light rays, so that substantially all reflections willbe eliminated, and at the same time serves as an insulating layer thatkeeps heat away from those metal walls.

The accompanying drawing illustrates my invention, in connection withone well-known type of photographic enlarger. Fig. .1 is a verticalcentral section through such enlarger, in its complete form; and Fig. 2is a fragmentary vertical section through the upper part of the mainbody of the casing, showing on the right-hand side the wall coated withan adherent coating before the insulating material is applied, andshowing on the left-hand side the wall carrying the complete coating,with the flocculent material in place on top of and integrally united tothe preliminary adherent coating.

The photographic enlarger shown has a main casing-body III, tape ringdownward and provided at its lower end with an inturned flange II onwhich rests a condensing lens I2. This main casing body is suitablysupported as by an arm I3 of which only a fragment is shown. At theupper end of the main casing body In there is removably mounted, in abell socket, a lamp housing I4, carrying an upwardly extendingventilator tube I5 in which is mounted in any suitable way (not shown) alamp socket I6 carrying a lamp bulb II. The upper end of the ventilatortube I5 is provided with a cover I8 having a central opening I9 throughwhich a lamp cord (not shown) may extend and with various other openings20 through which heated air may escape.

The lower end of the main casing body II! may have a slot for receivinga negative carrier 2|, and below that it carries a downward tubularextension 22 which in turn carries in any suitable manner an objectivelens 23 here shown to be mounted at one end of the lens-carrying barrel24 which is screw-mounted in the tubular extension 22 so that it may beturned end for end in such tubular extension if desired.

As so far described, the enlarger is one nowstandard form of enlarger.

In such an enlarger, in the absence of my invention, there is a tendencyfor the light rays from the lamp IT to be reflected from the innersurfaces of the walls of the housing in which the lamp is located, sothat each point of reflection serves as a source of light, which in manyinstances tends to fog the picture. In addition, without my invention,the heat from the lamp I'I causes the enlarger to become excessively hotso that the negatives used in the negative carrier ZI curl and buckleand are often permanently damaged.

My present invention overcomes both of these difficulties. According tothat invention, I apply to the entire inner walls of the enlarger,desirably of all the parts I0, I4, I5, I8, 22, and 24, a coating 25 ofan adhesive heat-resisting material, conveniently a heat-resisting paintor varnish, desirably dark in color, as is indicated at the right-handside of Fig. 2. While that coating 25 is still tacky, I apply to it acoating of substantial thickness of a black flock 26, which may beflocculent cotton or mineral wool or flocculent glass or some otherflocculent insulating material. By reason of the tackiness of thepreliminary adhesive coating 25 at the time this flock is applied, theflock adheres to the preliminary coating, and is held firmly in place asthat coating dries. The fiock is most conveniently applied with a spraygun. The layer of flock is not smooth internally, where it is exposed tothe light and heat rays, but is fuzzy in character with a dull velvetytexture; so that air is entrapped among the short individual inwardlyprojecting filaments of the flock.

By reason of the black character of the flock, and its dull velvetysurface no substantial reflection occurs from the inner surfaces of thelamp housing, and the light rays which pass downward through the lensesI2 and 23 may be only the direct rays from the light bulb, instead ofhaving mixed with them great numbers of chance rays. The presence of theflock lining, moreover, greatly reduces the heating of the enlargerwalls, especially-at the position of the negative carrier. It isbelieved that this is because of the insulating effect of the flockcoating on the walls and of the fact that the flock coating preventsreflection of heat waves to the lower portions thereof near the negativeposition, so that less heat is transmitted along the walls to thoseportions and substantially no heat reaches the surfaces of thoseportions by reflection from other portions of the walls.

It has been found that after one-half hour of continuous operationwithout the flock coating the lamp housing walls reach a temperature 131F. above room temperature and the walls at the negative position reach atemperature 55 F. above room temperature. With the flock coating,however, under otherwise identical conditions, the lamp housing wallsreach a temperature 122 F. above room temperature and the walls near thenegative a temperature only 30 above room temperature. There is thus notonly a smaller temperature rise over all, but the temperature rise atthe negative position is reduced by almost half, and reduced much morethan at the lamp housing. The effect is therefore especially valuable,since it is especially important to reduce the negative temperature toavoid damage to the negative.

I claim as my invention:

1. A photographic enlarger, having a housing in which a lamp may bemounted and which may carry one or more lenses, the walls of whichhousing are provided internally with a layer of heat-resistant adhesivematerial to which is attached a layer of heat-insulating flock.

2. A photographic enlarger, having a housing in which a lamp may bemounted and which may carry one or more lenses, the walls of whichhousing are provided internally with a layer of heat-resistant adhesivematerial to which is attached a layer of non-reflecting andheat-insulating flock.

3. A photographic enlarger, having a housing in which a lamp may bemounted and which may carry one or more lenses, the walls of whichhousing are provided internally with a layer of heat-resistant adhesivematerial to which is attached a layer of non-reflecting flock.

4. A photographic enlarger, having a housing in which a lamp may bemounted and which may carry one or more lenses, the walls of whichhousing are provided internally with a coating of heat-insulating,non-reflecting flocculent material.

5. A photographic enlarger, having a housing in which a lamp may bemounted and which may carry one or more lenses, the Walls of whichhousing are provided internally with a coating of heat-insulating,non-reflecting flocculent material of black color.

6. A photographic enlarger, having a housing, means carried by thehousing for receiving a negative, and a support for a lamp in saidhousing at a point spaced from said negative receiver, said housingbeing provided internally with a layer of material which isnon-reflecting to both heat and light.

ELWOOD C. ROGERS.

